From: Minchan Kim <minchan@kernel.org>
To: Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>
Cc: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>,
Andrew Morton <akpm@linux-foundation.org>,
Joonsoo Kim <js1304@gmail.com>,
linux-mm@kvack.org, linux-kernel@vger.kernel.org
Subject: Re: [RFC][PATCH v2 3/3] mm/zsmalloc: increase ZS_MAX_PAGES_PER_ZSPAGE
Date: Mon, 22 Feb 2016 10:34:42 +0900 [thread overview]
Message-ID: <20160222013442.GB27829@bbox> (raw)
In-Reply-To: <20160222004758.GB4958@swordfish>
On Mon, Feb 22, 2016 at 09:47:58AM +0900, Sergey Senozhatsky wrote:
> On (02/22/16 09:25), Minchan Kim wrote:
> [..]
> > I tempted it several times with same reason you pointed out.
> > But my worry was that if we increase ZS_MAX_ZSPAGE_ORDER, zram can
> > consume more memory because we need several pages chain to populate
> > just a object. Even, at that time, we didn't have compaction scheme
> > so fragmentation of object in zspage is huge pain to waste memory.
>
> well, the thing is -- we end up requesting less pages after all, so
> zsmalloc has better chances to survive. for example, gcc5 compilation test
Indeed. I saw your test result.
>
> BASE
>
> 168 2720 0 1 115833 115831 77222 2
> 190 3072 0 1 109708 109707 82281 3
> 202 3264 0 5 1910 1895 1528 4
> 254 4096 0 0 380174 380174 380174 1
>
> Total 44 285 1621495 1618234 891703
>
>
> PATCHED
>
> 192 3104 1 0 3740 3737 2860 13
> 194 3136 0 1 7215 7208 5550 10
> 197 3184 1 0 11151 11150 8673 7
> 199 3216 0 1 9310 9304 7315 11
> 200 3232 0 1 4731 4717 3735 15
> 202 3264 0 1 8400 8396 6720 4
> 206 3328 0 1 22064 22051 17927 13
> 207 3344 0 1 4884 4877 3996 9
> 208 3360 0 1 4420 4415 3640 14
> 211 3408 0 1 11250 11246 9375 5
> 212 3424 1 0 3344 3343 2816 16
> 214 3456 0 2 7345 7329 6215 11
> 217 3504 0 1 10801 10797 9258 6
> 219 3536 0 1 5295 5289 4589 13
> 222 3584 0 0 6008 6008 5257 7
> 223 3600 0 1 1530 1518 1350 15
> 225 3632 0 1 3519 3514 3128 8
> 228 3680 0 1 3990 3985 3591 9
> 230 3712 0 2 2167 2151 1970 10
> 232 3744 1 2 1848 1835 1694 11
> 234 3776 0 2 1404 1384 1296 12
> 235 3792 0 2 672 654 624 13
> 236 3808 1 2 615 592 574 14
> 238 3840 1 2 1120 1098 1050 15
> 254 4096 0 0 241824 241824 241824 1
>
> Total 129 489 1627756 1618193 850147
>
>
> that's 891703 - 850147 = 41556 less pages. or 162MB less memory used.
> 41556 less pages means that zsmalloc had 41556 less chances to fail.
Let's think swap-case which is more important for zram now. As you know,
most of usecase are swap in embedded world.
Do we really need 16 pages allocator for just less PAGE_SIZE objet
at the moment which is really heavy memory pressure?
>
>
> > Now, we have compaction facility so fragment of object might not
> > be a severe problem but still painful to allocate 16 pages to store
> > 3408 byte. So, if we want to increase ZS_MAX_ZSPAGE_ORDER,
> > first of all, we should prepare dynamic creating of sub-page of
> > zspage, I think and more smart compaction to minimize wasted memory.
>
> well, I agree, but given that we allocate less pages, do we really want to
> introduce this complexity at this point?
I agree with you. Before dynamic subpage chaining feature, we need
lots of testing in heavy memory pressure with zram-swap.
However, I think the feature itself is good to have in the future. :)
>
> -ss
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next prev parent reply other threads:[~2016-02-22 1:34 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-02-21 13:27 [RFC][PATCH v2 0/3] mm/zsmalloc: increase objects density and reduce memory wastage Sergey Senozhatsky
2016-02-21 13:27 ` [RFC][PATCH v2 1/3] mm/zsmalloc: introduce zs_get_huge_class_size_watermark() Sergey Senozhatsky
2016-02-21 13:27 ` [RFC][PATCH v2 2/3] zram: use zs_get_huge_class_size_watermark() Sergey Senozhatsky
2016-02-22 0:04 ` Minchan Kim
2016-02-22 0:40 ` Sergey Senozhatsky
2016-02-22 1:27 ` Minchan Kim
2016-02-22 1:59 ` Sergey Senozhatsky
2016-02-22 2:05 ` Sergey Senozhatsky
2016-02-22 2:57 ` Minchan Kim
2016-02-22 3:54 ` Sergey Senozhatsky
2016-02-22 4:54 ` Minchan Kim
2016-02-22 5:05 ` Sergey Senozhatsky
2016-02-21 13:27 ` [RFC][PATCH v2 3/3] mm/zsmalloc: increase ZS_MAX_PAGES_PER_ZSPAGE Sergey Senozhatsky
2016-02-22 0:25 ` Minchan Kim
2016-02-22 0:47 ` Sergey Senozhatsky
2016-02-22 1:34 ` Minchan Kim [this message]
2016-02-22 2:01 ` Sergey Senozhatsky
2016-02-22 2:34 ` Minchan Kim
2016-02-22 3:59 ` Sergey Senozhatsky
2016-02-22 4:41 ` Minchan Kim
2016-02-22 10:43 ` Sergey Senozhatsky
2016-02-23 8:25 ` Minchan Kim
2016-02-23 10:35 ` Sergey Senozhatsky
2016-02-23 16:05 ` Minchan Kim
2016-02-27 6:31 ` Sergey Senozhatsky
2016-02-22 2:24 ` Sergey Senozhatsky
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